1. Field of the Invention
The present invention relates to a power storage device. In particular, the present invention relates to a power storage device which is charged with electric power through an electromagnetic wave. Furthermore, the present invention relates to a charging system using a power storage device provided with an antenna and a power feeder which supplies electric power to the power storage device through an electromagnetic wave.
A “power storage device” mentioned in this specification refers to a general device which stores electric power by an electromagnetic wave transmitted from an external power supply device (power feeder). In addition, a battery which stores power by wireless reception of an electromagnetic wave is referred to as a wireless battery (RF battery: Radio Frequency Battery).
2. Description of the Related Art
Various electronic appliances are coming into wide use, and a wide variety of products are on the market. In particular, in recent years, the spread of portable electronic appliances has been marked. For example, mobile phones, digital video cameras, and the like have become very convenient because of high-definition display portions, increased durability of batteries, and further reduction in power consumption of the batteries. A portable electronic appliance has a structure in which a battery that is a power storage means is built in. Thus, a power supply for driving the portable electronic appliance is secured by the battery. As matters now stand, as the battery, a battery such as a lithium ion battery is used, and the battery is directly charged from an AC adaptor which is plugged into a household AC power supply that is a power supply means.
Moreover, in recent years, development of a power storage device which stores electric energy wirelessly so that a portable appliance can be charged also in a place without a commercial power supply has been advanced (e.g., see Patent Document 1: Japanese Published Patent Application No. 2003-299255).